New code for 5.4:
- Remove KM_SLEEP/KM_NOSLEEP.
- Ensure that memory buffers for IO are properly sector-aligned to avoid
  problems that the block layer doesn't check.
- Make the bmap scrubber more efficient in its record checking.
- Don't crash xfs_db when superblock inode geometry is corrupt.
- Fix btree key helper functions.
- Remove unneeded error returns for things that can't fail.
- Fix buffer logging bugs in repair.
- Clean up iterator return values.
- Speed up directory entry creation.
- Enable allocation of xattr value memory buffer during lookup.
- Fix readahead racing with truncate/punch hole.
- Other minor cleanups.
- Fix one AGI/AGF deadlock with RENAME_WHITEOUT.
- More BUG -> WARN whackamole.
- Fix various problems with the log failing to advance under certain
  circumstances, which results in stalls during mount.